Submitter here. The only cringeworthy mistake I see in the grammar was my insertion of a superfluous subject complement in the second sentence (extra "that" in bold below), esp. in terms of flow from the first sentence. What others am I missing? Full summary below:
Yahoo is running an A/B test that blocks access to Yahoo email if the site detects that the user is running an Ad Blocker. Yahoo says that this a trial rather than a new policy, effecting only a "small number" of users. Those lucky users are greeted with a message that reads "Please disable Ad Blocker to continue using Yahoo Mail." Regarding the legality of the move, "Yahoo is well within its rights to do so," said Ansel Halliburton an attorney at Kronenberger Rosenfeld who specializes in Internet law.